Project abstract Animals, including humans, interact with their environment via self-generated and continuous actions that enable them to explore and subsequently experience the positive and negative consequences of their actions. As a result of their interactions with the environment, animals alter their future behavior, typically in a manner that maximizes positive and minimizes negative outcomes. Furthermore, how an animal interacts with its environment and the actions that it chooses depend on its current environment, its past experience in that environment, as well as its internal state. Thus, the actions taken by an animal are dynamic and evolving, as necessary for behavioral adaptation. It is thought that both the execution of actions, in particular goal-oriented actions, and the modification of future behavior in response to the outcome of actions, depend on evolutionarily old parts of the brain called the basal ganglia. Within the basal ganglia, cells that produce dopamine have a profound influence on behavior, including human behavior, and their activity appears to encode for features of the environment and animal experience that are important for directing goal-oriented behavior. Here we bring together a team of experimental and computational neurobiologists to understand how these dopamine- producing cells modulate behavior and basal ganglia circuitry. We will use unifying theories and models to integrate information acquired over many classes of behavior. Completing the proposed work, including the technical advances and biological discoveries, will provide a platform for future analyses of related circuitry and behaviors in many species, including humans.